Single Unix Specification
The Single Unix Specification, also known as SUS, is a group of operating system standards that define what kind of operating system can officially be given the name "Unix". The standards started being developed in the 1980s when organizations needed a way to ensure that their software could be re-used on multiple Unix platforms. Today, the SUS guarantees that certain commands do the same thing on different systems, and is crucial to developers and end users alike.
SUS compliant operating systems
The SUS is currently defined and maintained by the Austin Group, a subset of the Open Group. Operating systems that are compliant with the Single Unix Specification include: